A systematic review of directions in animal enclosure use studies

Enclosure use research is important for better understanding the needs and preferences of animals under captive care. As such, enclosure use is often assessed in tandem with behavioural observations as part of holistic welfare assessments. Although valuable as a welfare tool, there are several inherent challenges in enclosure use research, including variability in zones, resource sizes and observation lengths, with several indices developed to account for these challenges. Nonetheless, it is unclear the extent to which these enclosure use indices are commonly used in published literature. Therefore, it is important that the role of these indices in welfare research be quantified and reviewed, with a view to understanding the needs of enclosure use researchers. In addition, although one enclosure use review has been previously published, the work was not systematic in its approach, and there is a need for updated research given the changes in technology since its publication. To identify the current index, topics and species focuses, we conducted a systematic review of enclosure use literature, using several search engines. A total of 4275 papers were identified: following filtering 169 papers remained, which investigated 260 species-level studies. The review identified relatively few published publications before the turn of the millennium, with most papers published since 2004. In addition, 2023 had the most enclosure use-based publications, with a total of 21 papers found. The most common topics under study were visitor effects and enrichment, which demonstrates that much of the enclosure use literature is motivated by welfare-related questions. Most papers used no stated formal enclosure use index, which may pose challenges in terms of research design and interpretation. There was limited crossover in terms of index use between different industries, such as laboratories, agriculture and zoos. Additionally, over half of the identified studies focused on a mammalian species, whereas fish and invertebrate studies were identified infrequently. This systematic review demonstrates that there is need to share knowledge and enclosure use methodologies between industries, and focusing on a greater diversity of taxa would aid in improving overall species welfare and husbandry knowledge.